Aqueous adhesive dispersions and the use thereof in the production of multi-layered paper

ABSTRACT

The invention relates to aqueous adhesive dispersions containing A) 0.1-10 wt. % adhesive polymer in the form of a dispersion with respect to the overall weight of the dispersion, B) 0.1-100 parts by weight of constituent A), an anionic or cationic polyelectrolyte and C) 0-50 parts by weight in relation to the 100 parts by weight of constituents A) of at least one polyalkyleneglycol with a molar mass of 200-100,000 g/mol. The invention also relates to the use of said dispersions in the production of multi-layered paper or paper material.

[0001] The invention relates to aqueous adhesive dispersions and to aprocess for producing multilayered paper, cardboard and carton havingimproved layer and ply strength, using said adhesive dispersions.

[0002] Multilayered papers are obtained from paper pulp mixtures of sameor different composition by compressing (couching) the wet paper webs.Essentially, the quality of multilayered packaging papers or cartons isdetermined by the internal strength of these materials, the cohesion inthe interface region between the individual plies of paper representinga weak point, however. Therefore, adhesive starch or starch derivativesare frequently used to improve the layer and ply strength. When exposedto major shear forces, heat or increased moisture during storage andfurther processing, however, stability may be lost even in productsproduced in this fashion, and the material may undergo breaking.

[0003] To date, native or modified starch in the form of an aqueousdispersion is sprayed as adhesive onto or between the paper plies,undergoing gelatinization in the drying section of the paper machine,thereby effecting bonding of the plies. Frequently, however, the layerand ply strength achieved in this manner is limited, particularly inthose cases where the starch bonding undergoes complete or partialirreversible embrittlement during subsequent heat exposure. According toF. Andruchovici and R. Wilken, PTS-Verlag Munich, 1994,PTS-Forschungsbericht, PTS-FB 09/93, p. 19, the use of native starch isdisadvantageous in that native starch can be employed with only lowsolids content due to its rheological characteristics (high viscosity),while the exclusive use of cationic starch is disadvantageous for costreasons.

[0004] According to EP-B-310,078, an adhesive composition of stableviscosity on the basis of gelled particulate starch is used in theproduction of corrugated cardboard, which starch is employed togetherwith a polymeric thickening agent of basic reaction, such as anacetone-formaldehyde resin, in the form of an aqueous dispersion.

[0005] A concentrated starch glue for the production of corrugatedcardboard is known from DE-A-44 01 529, which includes an ionicsurfactant to reduce its viscosity.

[0006] According to EP-B-415,385, surface and web strength and tearresistance of paper and cardboard are achieved by spraying the wet paperwebs with a slurry of non-gelled starch grains having a gel temperatureof 35-55° C., previously obtained by heating a mixture of crude starch,urea, phosphoric acid or a phosphate at a temperature of 80-150° C. fora period of from 0.5 to 5 hours.

[0007] Other paper sizing agents are known from EP-A-742,316, whichagents include cationized starch preferably esterified with unsaturateddicarboxylic acids or anhydrides.

[0008] These well-known adhesives can only be produced with hightechnical input and have an adhesive effect that is insufficient formany applications.

[0009] Likewise, the use of polyacrylamide instead of starch asstrengthening agent in spray coating, as described by K. Sato in JapanTappi Journal 49, 318-323 (1995), No. 2, is inappropriate.Alternatively, the product is employed in the form of a solution which,however, not only remains on the surface of the paper web afterspraying, but rather, penetrates therein.

[0010] Furthermore, a process for producing an abrasion-resistantdecorative laminate is known from EP-B-555,093, wherein an aqueousslurry of aluminum oxide particles and a high molecular weight cationicretention agent such as polyacrylamide is coated on the uppermost wetlayer of paper material and then subjected to further conventional papermanufacturing.

[0011] EP-B-606,431 describes a composition for coating cardboard,containing cationic starch and a vinyl acetate polymerization productwhich are also coated together with pigments. As is well-known, however,laminating of paper sheet materials involves other requirements ascompared to the production of multilayered paper per se.

[0012] It was therefore the object to provide an adhesive dispersionthat would enable easy production of multilayered paper with improvedproperties, particularly with enhanced layer and ply strength.

[0013] Said object is accomplished by providing the aqueous adhesivedispersions according to the invention, containing

[0014] A) 0.1-10 wt.-%, preferably 2-6 wt.-%, relative to the overallweight of the dispersion, of an adhesive polymer in dispersed form,

[0015] B) 0.1-100 parts by weight, preferably 0.1-20 parts by weight,more preferably 0.1-10 parts by weight, relative to 100 parts by weightof component A), of at least one anionic or cationic polyelectrolyte,and

[0016] C) 0-50 parts by weight, preferably 0.1-30 parts by weight, morepreferably 0.1-20 parts by weight, relative to 100 parts by weight ofcomponent A), of at least one polyalkylene glycol having a molar massranging from 200 to 100,000 g/mol.

[0017] At least one natural or synthetic adhesive polymer, preferably apolysaccharide, an optionally modified polysaccharide, a protein, and/ora polyvinyl alcohol is used as component A), which polymer is present indispersed form in said dispersion, i.e., has not been heated above itsgelatinization temperature.

[0018] It is particularly preferred to use starch, modified starch,cellulose ethers such as carboxymethylcellulose, polyvinyl alcohols,alginates, proteins such as glutin, casein, and/or guar meal as adhesivepolymers. However, starch and/or starch derivatives are preferred foreconomic reasons.

[0019] In this context, native starch, such as potato starch, wheatstarch, corn starch, rice starch, pea starch and/or mixtures thereof,modified starches such as starch degradation products, particularlydextrins, chemically modified starches such as substituted starchderivatives and especially anionic starches such as dialdehyde starch,carboxystarch, and starch degraded by persulfate, anionic starch esterssuch as starch phosphoric acid mono- or di-esters, starch acetates andstarch citrates, anionic starch ethers such as carboxymethylstarch,carboxymethyl-2-hydroxyethylstarch, andcarboxymethyl-3-hydroxypropylstarch, and cationic starch derivativessuch as N-containing starch ethers, particularly starches having primaryor secondary amino or imino groups, and tertiary amino groups positivelycharged by protonation with acids, and quaternary ammonium groups areused.

[0020] The cationic or anionic polyelectrolytes to be used as componentB) according to the invention are selected from the group of syntheticor optionally modified natural polymer products. Preferably, they arewater-soluble or water-swellable cationic or anionic synthetic homo- orco-polymers of monoethylenically unsaturated monomers with acid groupswhich at least partially are present as salts, or their esters withdi(C₁-C₂)alkylamino(C₂-C₆)alkylalcohols, or their amides withdi(C₁-C₂)alkylamino(C₂-C₆)alkylamines as reported in EP-A-0,013,416 orin EP-A-0,113,038, each one being used in protonated or quaternizedform, and optionally other monoethylenically unsaturated monomers.

[0021] These polyelectrolytes are remarkable in that they do not act asa flocculant for component A) below the gelatinization temperaturethereof, but rather, form stable aqueous dispersions with A).

[0022] Preferably, homopolymers or copolymers of water-soluble,monoethylenically unsaturated vinyl compounds, such as acrylic acid andmethacrylic acid esters of dialkylaminoalkylalcohols in protonated orquaternized form, such as dimethylaminoethyl acrylate, acrylic acid andmethacrylic acid amides of dialkylaminoalkylamines, in protonated orquaternized form, such as acrylamidopropyltrimethylammonium chlorideand/or acrylamidopropyltrimethylammonium methyl methosulfate can be usedas cationically active polyelectrolytes.

[0023] Furthermore, Mannich bases of polymers containing acrylamide,polyvinylamines, polyamines such as diethyleneamine,dipropylenetriamine, triethylenetetramine, and polyalkylenepolyamines(polyethyleneimines) with molar masses of from 450 to 100,000 g/mol,preferably liquid polyalkylenepolyamines with molar masses of from 450to 20,000 g/mol or solutions thereof in water are suitable as cationicpolyelectrolytes.

[0024] In case the dispersions according to the invention do not includeany component C, only those polymer products are possible—when usingpolymers as cationic polyelectrolytes—that do not include any aldehydeor methylol groups as functional groups.

[0025] Preferably, homo- and/or copolymers of monoethylenicallyunsaturated carboxylic acids and sulfonic acids, such as acrylic acid,methacrylic acid, maleic acid, itaconic acid, crotonic acid and/or thealkali, preferably sodium, potassium or ammonium salts thereof,vinylsulfonic acid, acrylamido- and methacrylamidoalkanesulfonic acidssuch as 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethylmethacrylate, and styrenesulfonic acid, and/or the alkali, preferablysodium or potassium or ammonium salts are suitable as anionicpolyelectrolytes.

[0026] Furthermore, vinylphosphonic acid and styrenephosphonic acid, aswell as the alkali salts, preferably the sodium or potassium or ammoniumsalts thereof are suitable.

[0027] The copolymers can be formed using the above-mentioned ionicmonomers and non-ionogenic, water-soluble, monoethylenically unsaturatedmonomers such as acrylamide, methacrylamide, N-(C₁-C₂)alkylated(meth)acrylamides, as well as N-vinylamide, vinylformamide,N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinylpyrrolidone. Inaddition, suitable water-soluble monomers are N-methylolacrylamide,N-methylolmethacrylamide, as well as N-methylol(meth)acrylamidespartially or completely etherified with monohydric C₁-C₄ alcohols, anddiallyldimethylammonium chloride.

[0028] Likewise, the copolymers may include limited amounts of sparinglywater-soluble and/or water-insoluble monoethylenically unsaturatedmonomers such as (meth)acrylic acid alkyl esters and vinyl acetate, aslong as the solubility or swellability of the copolymers in water isretained.

[0029] Moreover, the polymers products can be produced usingcrosslinking monomers having at least two reactive sites, preferablydiethylenically unsaturated monomers, so as to have swellability or onlylimited solubility in water, or they may consist of water-soluble andwater-swellable polymers.

[0030] According to the invention, water-soluble or water-swellableamphiphilic copolymers produced of cationic and anionic monomers mayalso be used.

[0031] Furthermore, melamine-formaldehyde condensation products andurea-formaldehyde condensation products in anionic and cationicmodification, polyamidoamine-epichlorohydrin resins, e.g. the reactionproducts of adipic acid with dieethylenetriamine, or of similar aminesand epichlorohydrin are suitable as component B).

[0032] The polyelectrolytes used according to the invention can be mixedwith the adhesive polymers as a powder, dispersion or solution,preferably as an aqueous solution.

[0033] The weight ratio of the amounts of components A) and B), relativeto the total amount of components A) and B), preferably ranges from 4:1to 25:1, more preferably from 10:1 to 25:1, with a range of from 14:1 to20:1 being particularly preferred.

[0034] Furthermore, the adhesive dispersions of the invention mayadditionally include other additives such as surfactants, wet-strengthagents, sizing agents, hygroscopic agents, and pigments.

[0035] The adhesive dispersions are produced by combining the polymerand polyelectrolyte components, the components being placed in a vesselin any order, in portions or continuously in an aqueous phase,preferably as an aqueous dispersion, mixed by stirring or pumping, andoptionally heated below the gelatinization temperature of component A).The adhesive polymer A) is heated at a temperature below thegelatinization temperature, namely, at 30-55° C., preferably 35-50° C.,more preferably 40-45° C., and simultaneously or subsequently added witha solution or dispersion of the polyelectrolyte of optionally the sameor optionally the opposite ionogenicity. optionally, the dispersion canbe heated to the maximum temperature below the gelatinizationtemperature for a certain period of time.

[0036] The addition of polyalkylene glycol to the dispersion can beeffected as such or in the form of an aqueous solution of thepolyalkylene glycols prior to or subsequent to adding component A) orpreferably subsequent to adding component B). Heating of the dispersion,particularly the duration thereof, and the pH value of the aqueousdispersion can be determined by a person skilled in the art using simpletests depending on the raw materials used and the equipment-relatedconditions present and are selected in such a way that thegelatinization temperature of the components will not be exceeded. Byadding the polyelectrolytes B) to component A) and heating thedispersion, the condition of the homogeneous dispersions is retained.

[0037] Heating of the dispersion may also be effected in such a way thatthe components are heated one by one or placed in preheated water.

[0038] The production of multilayered paper is well-known and iseffected using paper machines equipped with multilayer screen sections,on which multiple paper webs are formed. To this end, rotary screensarranged in a well-known fashion, rotary screen molds, or an endlesswire section as sheet-forming system, consisting of e.g. 2-6 endlesswires, are used. Thereafter, the paper webs formed on the screensections are treated in wet condition with the adhesive dispersions ofthe invention, the adhesive being coated onto at least one paper web,the webs are contacted and subsequently combined to form a thicker web.When subsequently passing the drying section, final sizing of the paperwebs is effected using the adhesive dispersion.

[0039] Coating the adhesive dispersion onto at least one of the wetpaper webs can be performed using the well-known coating techniques asreported e.g. in F. Andruchovici and R. Wilken, PTS-Verlag Munich, 1994,PTS-Forschungsbericht, PTS-FB 09/93, p. 16. According to the invention,in particular, the spraying technique is preferred over concurrent orcountercurrent feed roll coating where wetting of the paper web can beeffected over the entire surface, or limited e.g. by templates. Toachieve sufficient sprayability of the adhesive dispersion,water-soluble polymers having a molecular weight m.w. (g/mol) of from1000 to 2 millions, preferably from 1000 to 100,000, and more preferablyfrom 1000 to 50,000 are preferably used as component B). Appropriatepolymer products are obtained in a well-known fashion by adjusting thepolymerization conditions, using suitable initiator and modifiercombinations. Furthermore, it is possible to start off with highmolecular weight polymer products and subject same to mechanicaldegradation, e.g. by shearing in aqueous solution, prior to combiningwith component A).

[0040] The adhesive dispersions according to the invention areremarkable for their excellent shelf-life when dispersed in aqueousphase.

[0041] When coating the adhesive dispersions of the invention, thedispersed portions precipitate on the surface or in the upper fibrousregion of the paper web. The combined wet paper webs then pass the presssection and subsequently the drying section of the paper machine wherebonding of the paper webs to be treated is effected under the conditionspresent therein to form a multilayered paper.

[0042] Therefore, the present invention is also directed to methods ofproducing multilayered papers and other sheet materials comprised ofpaper material and made up of at least 2 paper webs, using the adhesivedispersions according to the invention, particularly in manufacturingpackaging paper, corrugated cardboard, multi-web solid cardboard,carton, and multilayered test liner, as well as base paper forwallpapers, and other multilayered special papers remarkable for theirenhanced stability and strength, particularly with respect to layer andply strength.

[0043] Preferably, from 1 to 10 wt.-%, more preferably from 4 to 8wt.-%, relative to the paper production, of the aqueous dispersionaccording to the invention is used.

[0044] Without intending to be limiting, the invention will be describedin more detail with reference to the following Examples.

[0045] The ply strength is the measured value of the strength between anouter layer and the remaining other layers of the paper.

[0046] The layer strength is the measured value in the center of amultilayered paper with symmetrical structure.

[0047] The measurement readings are obtained by separating andsubsequent pulling apart the paper layers, using a tensile strengthtester in accordance with ASTM F 904-91.

COMPARATIVE EXAMPLE 1

[0048] The production of a multilayered cellulose special paper isperformed on a paper machine having 4 rotary screens, producing a basepaper having a gram weight of about 270 g/m² made up of layers having aweight of 60-70 g/m². To increase the layer and ply strength, a 2%aqueous starch dispersion continuously produced from a cationic starchdesignated Emcat® C 12 (Emsland Stärke Company) in a dispersing tank issprayed in an amount of 6 wt.-%, relative to the paper production,between each of the wet paper layers. After passing the paper webthrough the drying section, a base paper having a ply strength of 1.735N/cm and a layer strength of 1.559 N/cm is obtained.

EXAMPLE 1

[0049] The production of a multilayered special paper is performed inthe same way as described in Comparative Example 1, using an anionicdigester starch designated Retamyl® AP (AVEBE Company) and the cationicPraestafix® HH (Stockhausen GmbH & Co. KG) instead of the above cationicstarch. The dispersion is produced by dispersing the anionic digesterstarch in water and adding the cationic polymer in an amount of 6 partsby weight, relative to the starch, with stirring to the dispersing tank.The aqueous dispersion is heated in the dispersing tank and maintainedat a constant temperature of 40-45° C. The dispersion is sprayed betweenthe layers of the wet paper webs in an amount of 6 wt.-%, relative tothe paper production. After drying, a base paper having a ply strengthof 1.900 N/cm and a layer strength of 1.640 N/cm is obtained.

[0050] In subsequent processing steps on the special paper, the paperweb is reheated, which reheating so far has normally resulted in anembrittlement of an adhesive layer consisting exclusively of starch.This process is simulated using a test wherein a paper sample is heatedat 130° C. for 30 minutes and maintained, and the layer strength ismeasured immediately after this heat treatment. Subsequently, the sampleis re-conditioned under normal conditions at 23° C. and 50% relativehumidity. The change in the paper properties during this process ismonitored by measuring the strength. The test results of the papersamples of Comparative Example 1 and Example 1 are summarized inTable 1. TABLE 1 Changes in layer strength [N/cm] prior to and afterheating and after re-conditioning of the sample 30 min/ Loss of Re-cond.Re-cond. Re-cond. Sample Immediately 130° C. strength (%) 5 min 15 min30 min Comparative 1.700 0.760 55.3 1.265 1.600 1.665 Example 1 1.7700.840 52.5 1.330 1.625 1.735 Ø 1.735 0.800 53.9 1.2975 1.613 1.700Example 1 1.865 1.025 45.0 1.365 1.665 1.770 Ø 1.935 1.095 43.4 1.4001.600 1.865 1.900 1.060 44.2 1.383 1.633 1.818

[0051] The paper of Example 1 has high layer strength which ismaintained even after heating, because embrittlement of the adhesive isprevented as a result of using the adhesive dispersions according to theinvention.

EXAMPLES 2 TO 7 AND COMPARATIVE EXAMPLE 2

[0052] In a laboratory test, two sheets having 100 g/m² each wereproduced on the sheet-forming device using a pulp mixture having acontent of 3 wt.-% of dry substance, diluted with tap water to make 1wt.-%. One wet sheet was stored on chromocardboard, while the second wetsheet on the sheet-forming screen was treated with 10 g of a 2 wt.-%adhesive dispersion by spraying with a spraying flask.

[0053] The adhesive dispersion for Comparative Example 2 had previouslybeen prepared from a cationic starch, product designation Emcat® C 12(Emsland Stärke Company), and for Examples 2 to 7 from anionic starcheswith the product designations Retamyl® AP and Aniofax® AP 25 (both fromAVEBE Company) and various cationic polyelectrolytes, where the weightratio of starch component to cationic polyelectrolyte was 16:1 eachtime, and the mixture was heated for 10 minutes to 30 and 40° C.,respectively.

[0054] Following spraying, both sheets were couched on a screen using aroll, and then dried for 15 minutes in a vacuum dryer at 95° C. Threetwo-layered sheets were produced each time, using an adhesivedispersion, the layer strength of which was determined afterconditioning the sheets at 23° C. and 50% relative humidity, orimmediately after heating for 30 minutes in a drying oven at 130° C. Thecompositions of the adhesive dispersions employed, and the measured dataof the strength determinations are illustrated in Table 2. TABLE 2Temperature Initial value Sample after (° C.) (cond. sam- heat treatm.after heating ple) 30 min/130° C. Loss the mixture N/cm N/cm % Comp. Ex.2 Emcat ® C 12 30 1.065 0.600 43.7 Example 2 Retamyl ® AP + 30 1.3751.000 27.3 Praestafix ® HH Example 3 Retamyl ® AP + 40 1.530 1.135 25.8Polyamin ® SK¹⁾ Example 4 Retamyl ® AP + 40 1.665 1.200 27.9Cartiofast ® PL²⁾ Example 5 Retamyl ® AP + 30 1.615 1.225 24.1Cartiofast ® 8106³⁾ Example 6 Retamyl ® AP + 40 1.400 1.000 28.6Cartafix ® DPR⁴⁾ Example 7 Aniofax ® AP 25 + 40 1.330 0.865 35.0Praestafix ® HH

EXAMPLE 8 AND COMPARATIVE EXAMPLE 3

[0055] In the production of test liner III, which is a paper andcorrugated cardboard paper classification of the European Association ofCorrugated Paper Manufacturers with a gram weight of 190 g/m², on thebasis of waste paper using an endless wire papermaking machine, the wetpaper webs produced on two endless wires were sprayed at a dry contentof 10-15 wt.-% with an aqueous adhesive dispersion comprised of anionicstarch (Retamyl® AP) and the cationic Praestafix® HH polymer at a ratioof 16:1 as above. The components were admixed with a 2 wt.-% aqueousadhesive dispersion and heated at a temperature of 40° C. At aproduction rate of 4 t/hour, 20 kg/hour of Retamyl® AP and 5 kg/hour ofPraestafix® HH were continuously employed, as compared to 20 kg/hour ofa modified wheat starch (Comparative Example 3). The treated webs werecontacted, couched at a speed of 200 to 250 m/min, and subsequentlycompressed as one web and dried. Using production samples, the burstingpressure was measured according to ISO 2758 (1983), and the tearresistance and water-absorbing capacity of the sizing were determined(Cobb Method, ISO 535 (1991)). The measured data are illustrated inTable 3. TABLE 3 Test liner III, 190 g/m², PM 2 Duplex Bursting TearWater absorption pressure resistance g/m² [kPa] [J/m] [Cobb 60 s]Comparative 512 272 25 Example 3 Example 8 532 370 27

[0056] In addition to the marked improvement in tear resistance by 36%,the bursting strength is also favorably biased. In contrast, the sizing(or water absorption) is not significantly changed.

EXAMPLE 9 TO 15 AND COMPARATIVE EXAMPLE 4

[0057] Using a pulp mixture with a content of 2.9 wt.-%, two-layeredsheets were produced in analogy to the procedures of Examples 2 to 7,using aqueous adhesive dispersions according to the invention. Thedispersions were obtained by heating a dispersion of cationic starch(Emcat® C 12) and the cationic Praestafix® HH polymer, or the cationicpolymer product A 6309, or the anionic copolymer of acrylamide andsodium acrylate, Praestamin® AL (both from Stockhausen GmbH & Co. KG),or by heating dispersions of anionic starch (Retamyl® AP) and the sameabove-mentioned polyelectrolytes, or by heating a dispersion of Mowiol®28-99/G2 with Praestafix® HH, or of Walocel® XC 3.000 G with Praestamin®AL. Each of these products was employed at a ratio of 16:1, relative tothe ratio of adhesive polymer to polyelectrolyte. Comparative Example 4was produced in analogy to Comparative Example 2, using Emcat® C 12alone.

[0058] Again, the layer strength was determined after heating in adrying oven at 130° C. in comparison to a paper sample produced usingEmcat® C 12 alone. The measured data are illustrated in Table 4. TABLE 4Sample Initial value after heat Temperature (cond. sam- treatm. (° C.)ple) 30 min/130° after heating N/cm C. Loss the mixture 22° C. N/cm %Comp. Ex. 4 Emcat ® C 12 30 0.800 0.425 46.9 Example 9 Retamyl ® AP + 401.735 1.265 27.1 Praestafix ® HH Example 10 Retamyl ® AP + 40 1.6001.265 20.9 Product A6309¹⁾ Example 11 Emcat ® C 12 + 40 0.760 0.535 29.6Praestafix ® HH Example 12 Emcat ® C 12 + 40 0.720 0.495 31.3 ProductA6309¹⁾ Example 13 Emcat ® C 12 + 40 0.720 0.505 29.9 Praestamin ® A1¹⁾Example 14 Mowiol ® 28-99/G2²⁾ 40 1.200 0.865 27.9 Praestafix ® HHExample 15 Walocel ® XC3.000G³⁾ 40 1.530 1.200 21.6 Praestafix ® HH

EXAMPLES 16-21 AND COMPARATIVE EXAMPLES 5-10

[0059] The adhesive dispersions were produced by introducing theRetamyl® AP anionic starch in water with stirring; the water hadpreviously been heated at 40° C. Thereafter, 0.125 wt.-% of thePraestafix® HH cationic polymer and the polyalkylene glycols Polyglycol300 (Contensio Chemicals GmbH) and Polyglycol 10000S (Clariant GmbH),respectively, were added one by one, likewise with stirring.

[0060] In Comparative Examples 5-10, the adhesive dispersion wasproduced from the conventionally used Emcat® C12 cationic starch, withaddition of Polyglycol 300 and Polyglycol 10000S, respectively.

[0061] The sole use of an anionic starch, or of a combination of ananionic starch with polyalkylene glycol in the industrial production ofmultilayered paper is not possible because—as taught by experience—thepaper layers undergo displacement already on the paper machine.

[0062] Using a pulp mixture with a content of 2.9 wt.-%, two-layeredsheets were produced in analogy to the procedure of Examples 2-7, usingthese adhesive dispersions.

[0063] The compositions of the adhesive dispersions and the ascertaineddata regarding the layer strength of the multilayered sheets at 23° C.and after treating the sheets for 30 min at 130° C. are summarized inthe following Table 5. The quantity figures in % by weight refer to thepulp mixture dry matter. TABLE 5 After 30 min 23° C. at 130° C. N/cmN/cm Examples 16* 2.0% Retamyl ® AP + 0.1% 1.840 1.310 Polyglycol 30017* 2.0% Retamyl ® AP + 0.2% 2.065 1.375 Polyglycol 300 18* 2.0%Retamyl ® AP + 0.4% 1.775 1.200 Polyglycol 300 19* 2.0% Retamyl ® AP +0.1% 1.600 1.040 Polyglycol 1000S 20* 2.0% Retamyl ® AP + 0.2% 1.3850.935 Polyglycol 1000S 21* 2.0% Retamyl ® AP + 0.4% 1.665 1.015Polyglycol 1000S Comparative Examples  5  2.0% Emcat ® C12 + 0.1% 0.7350.455 Polyglycol 300  6  2.0% Emcat ® C12 + 0.2% 0.600 0.420 Polyglycol300  7  2.0% Emcat ® C12 + 0.4% 0.600 0.395 Polyglycol 300  8  2.0%Emcat ® C12 + 0.1% 0.600 0.380 Polyglycol 10000S  9  2.0% Emoat ® C12 +0.2% 0.655 0.385 Polyglycol 10000S 10  2.0% Emcat ® C12 + 0.4% 0.5050.400 Polyglycol 10000S

EXAMPLES 22-25

[0064] Further adhesive dispersions were produced in analogy to theproduction procedure of Examples 16-21 using the Retamyl® AP anionicstarch wherein, in addition to the Praestafix® HH cationic polymer, amodified melamine-formaldehyde resin from Vianova Resins Company,designated Madurit® MW114 30% WA TZ, or a polyamideamine-epichlorohydrinresin from BK Giulini Chemie Company, designated Giluton 1100/28 N, wereused as component B), and each of these resins were used as component B)alone with Polyglycol 300. The addition of Polyglycol 300 was effectedafter adding the cationic polyelectrolytes to the starch dispersed inwater.

[0065] Using a pulp mixture with a content of 2.9 wt.-%, two-layeredsheets were produced in analogy to the procedure of Examples 2-7, usingthese adhesive dispersions. The compositions of the adhesive dispersionsand the data regarding the strength are illustrated in Table 6. Thequantity figures in % by weight refer to the pulp mixture dry matter.After 30 min at 23° C. 130° C. Loss Examples N/cm N/cm % 22 2.0%Retamyl ® AP/ 1.735 1.200 30.8 0.125% Praestafix ® HH + 0.2% Madurit ®MW 114 23 2.0% Retamyl ® AP/ 1.495 1.000 33.1 0.125% Praestafix ® HH +0.1% Giluton ® N 1100/28 24 2.0% Retamyl ® AP/ 1.800 1.080 40.0 0.125%Madurit ® MW 114 + 0.2% Polyglycol 300 25 2.0% Retamyl ® AP/ 1.800 1.09539.2 0.125% Giluton ® N 1100/28 + 0.4% Polyglycol 300

EXAMPLES 26-29

[0066] In analogy to the procedure of Examples 2-7, adhesive dispersionswere produced at 40° C. from the Retamyl® AP anionic starch and thePraestafix® HH cationic polymer, using fractions of a specific grainsize of the starch particles in a range of from more than 200 μm to lessthan 63 μm. The figures regarding the composition of the adhesivedispersion in % by weight refer to the pulp mixture dry matter.Two-layered sheets were produced in accordance with the procedure ofExamples 2-7, using these adhesive dispersions. The data are summarizedin Table 7. TABLE 7 After 30 min at 23° C. 130° C. Examples N/cm N/cm 262% Retamyl ® AP >200 μm/ 1.360 1.135 0.125% Praestafix ® HH 27 2%Retamyl ® AP >100 μm/ 1.625 1.105 0.125% Praestafix ® HH 28 2% Retamyl ®AP >63 μm/ 1.935 1.240 0.125% Praestafix ® HH 29 2% Retamyl ® AP <63 μm/1.665 1.040 0.125% Praestafix ® HH

[0067] The adhesive dispersions according to the invention achieveimproved layer strength values when using the anionic starch with aparticle size ranging from 50 to 200 μm, preferably from 50 to 100 μm ascomponent A).

1. Aqueous adhesive dispersions, consisting of A) 0.1-10 wt.-%, relativeto the overall weight of the dispersion, of an adhesive polymer indispersed form, B) 0.1-100 parts by weight, relative to 100 parts byweight of component A), of an anionic or cationic polyelectrolyte, andC) 0-50 parts by weight, relative to 100 parts by weight of componentA), of at least one polyalkylene glycol having a molar mass ranging from200 to 100,000 g/mol, and optionally other additives.
 2. The adhesivedispersions according to claim 1, characterized in that the adhesivedispersions contain 2-6 wt.-% of component A), relative to the totalweight of the dispersion, and 0.1-20 parts by weight of component B),relative to 100 parts by weight of component A).
 3. The adhesivedispersions according to claim 1 or 2, characterized in that theadhesive dispersions contain 0.1-30 parts by weight, preferably 0.1-20parts by weight, relative to 100 parts by weight of component A), of atleast one polyalkylene glycol.
 4. The adhesive dispersions according toany of claims 1 to 3, characterized in that at least one natural orsynthetic polymer, preferably a polysaccharide, a modifiedpolysaccharide, a protein, and/or a polyvinyl alcohol is used ascomponent A).
 5. The adhesive dispersions according to claim 4,characterized in that native starch, modified starch, cellulose ethers,guar meal, alginates, proteins, and/or polyvinyl alcohol are used ascomponent A).
 6. The adhesive dispersions according to claim 5,characterized in that cationic or anionic starch is employed ascomponent A).
 7. The adhesive dispersions according to one or more ofclaims 1 to 6, characterized in that at least one polyethylene glycol isused as component C).
 8. The adhesive dispersions according to one ormore of claims 1 to 7, characterized in that component B) does not actas a flocculant below the gelatinization temperature of component A). 9.The adhesive dispersions according to one or more of claims 1 to 8,characterized in that at least one water-soluble or water-swellablecationic or anionic synthetic homo- or copolymer of monoethylenicallyunsaturated monomers having acid groups, which at least partially arepresent as salts or as esters or amides of dialkylaminoalkylalkanols or-amines in protonated or quaternized form, and optionally othermonoethylenically unsaturated monomers, Mannich bases of polymerscontaining acrylamide, polyvinylamines, polyamines, andpolyalkyleneamines having molar masses of from 450 to 100,,00 g/mol,melamine-formaldehyde condensation products, urea-formaldehydecondensation products in anionic and cationic modification, orpolyamidoamine-epichlorohydrin resins or mixtures thereof are used ascomponent B).
 10. The adhesive dispersions according to claim 9,characterized in that acrylic acid, methacrylic acid, maleic acid,itaconic acid, crotonic acid, and vinylsulfonic acid,(meth)acrylamidoalkanesulfonic acids, preferably2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl methacrylate,styrenesulfonic acid, vinylphosphonic acid, and/or styrenephosphonicacid, as well as their alkali or ammonium salts are present as recurringunits in the anionic homo- or copolymers as monoethylenicallyunsaturated monomers containing acid groups, and (meth)acrylic acidesters with dialkylaminoalkylalkanols or (meth)acrylic acid amides withdialkylaminoalkylamines in protonated or quaternized form are present asrecurring units in the cationic homo- or copolymers.
 11. The adhesivedispersions according to one or more of claims 1 to 10, characterized inthat component A) and component B) exhibit dissimilar ionogenicity. 12.A process for producing multilayered paper or a sheet materialconsisting of paper material and formed of at least 2 paper webs, bycoating an aqueous adhesive dispersion onto at least one paper web inwet condition, compressing and drying the combined paper webs,characterized in that a dispersion according to one or more of claims 1to 11 is used as adhesive dispersion.
 13. The process according to claim12, characterized in that the adhesive dispersion is sprayed onto atleast one paper web.